A light-emitting diode (LED) is suitable for diverse applications because it has good opto-electrical characteristics of low power consumption, low heat generation, long life, shock tolerance, compact, swift response, and stable output wavelength.
More applications are using infrared light-emitting diode nowadays. In addition to the conventional application in remote controllers and monitors, the application of the infrared light-emitting diode in smart phones and touch panels has been developed recently. Compared with other applications, because each touch panel adopts a relatively larger amount of infrared light-emitting diodes, lower price is required. Therefore, reducing the cost of an infrared light-emitting diode is necessary.
FIG. 1 shows a cross-sectional view of a conventional infrared light-emitting diode. As shown in FIG. 1, the light-emitting diode comprises a permanent substrate 101. A light-emitting stack 102, a metal reflective layer 103, a barrier layer 104, and a bonding structure 105 are disposed on the permanent substrate 101 from top to bottom. In addition, a first electrode 106E1 and its extending electrode 106E1′ is disposed on the light-emitting stack 102, and a second electrode 106E2 is disposed on the permanent substrate 101. The first electrode 106E1, the extending electrode 106E1′, and the second electrode 106E2 are used to provide current to the light-emitting diode. The light-emitting stack 102 emits infrared light. In the manufacturing process of this conventional infrared light-emitting device, the light-emitting stack 102 is originally grown on a growth substrate (not shown), and then the light-emitting stack 102 is bonded to the permanent substrate 101 by the bonding structure 105. Therefore, the metal reflective layer 103 may be formed on the light-emitting stack 102 before the bonding. However, as described above, in some applications, such as the application in touch panels which requires cost reduction, the aforementioned bonding process and the metal reflective layer 103 are the primary causes of high cost. In addition, in order to achieve a larger far field angle of light, more lateral light is required in the application of the touch panels. However, it has been found in reality it is difficult for the above conventional infrared light-emitting device to meet the requirement in this respect.